High-purity aluminum sputter targets and method of manufacture

ABSTRACT

The high-purity aluminum sputter target is at least 99.999 weight percent aluminum and has a grain structure. The grain structure is at least 99 percent recrystallized and has a grain size of less than 200 μm. The method forms high-purity aluminum sputter targets by first cooling a high-purity target blank to a temperature of less than −50 ° C. and then deforming the cooled high-purity target blank introduces intense strain into the high-purity target. After deforming, recrystallizing the grains at a temperature below 200 ° C. forms a target blank having at least 99 percent recrystallized grains. Finally, finishing at a low temperature sufficient to maintain the fine grain size of the high-purity target blank forms a finished sputter target.

This application is a divisional application of the U.S. Ser. No.10/219,756 filed on Aug. 16, 2002 and patented on Dec. 28, 2004, U.S.Pat. No. 6,835,251, which is a continuation-in-part application of theU.S. Ser. No. 10/054,345, filed on Nov. 13, 2001 and abandoned.

BACKGROUND OF THE INVENTION

There has been a great deal of work on the refinement of microstructuresbased on cold-working and recrystallizing heat treatments (annealing).Unfortunately, these techniques have experienced limited success forrefining pure aluminum microstructures. The highly-mobile grainboundaries in high-purity aluminum can allow spontaneous partialrecrystallization to occur at room temperature under normal, ambientworking conditions. In addition, high-purity aluminum does not have anyprecipitates or any significant amount of solute to provide the “Zenerdrag” necessary for effective retardation of grain boundary motion.Consequently, grain size is very difficult to control using conventionalthermomechanical processing methods.

Historically, pure aluminum sputter targets have been manufactured withrecrystallized grain sizes ranging typically from 500 μm to 5 mm. These“large” grain sizes can contribute to poor sputter uniformity. Inaddition, since these pure aluminum sputter targets have limitedstrength, they often require backing plates to control warping duringsputtering. In view of these problems, there is a desire to improve thestrength and sputtering performance for high-purity aluminum targets.

Target manufacturers have relied upon equal channel angular extrusion(ECAE) to produce fine grain microstructures. Nakashima et al.,“Influence of Channel Angle on the Development of Ultrafine Grains inEqual-Channel Angular Pressing,” Acta. Mater., Vol. 46, (1998), pp.1589-1599 and R. Z. Valiev et al., “Structure and Mechanical Behavior ofUltrafine-Grained Metals and Alloys Subjected to Intense PlasticDeformation,” Phys. Metal. Metallog., Vol. 85, (1998), pp. 367-377provide examples of using ECAE to reduce grain size. ECAE introduces anenormous strain into a metal without imparting significant changes inworkpiece shape. Although this process is effective for reducing grainsize, it does not appear to align grains in a manner that facilitatesuniform sputtering or provide an acceptable yield-the low yieldoriginates from the ECAE process operating only with rectangular shapedplate and thus, requiring an inefficient step of cutting circulartargets from the rectangular plate.

Another mechanical method for producing fine grain structures in metalsis “accumulative roll bonding” where aluminum sheets are repeatedlystacked and rolled to impart sufficient strain required for ultra-finegrain sizes. N. Tsuji et al., “Ultra-Fine Grained Bulk Steel Produced byAccumulative Roll Bonding (ARB) Process,” Scripta. Mater., Vol. 40,(1999), pp. 795-800. The repeated stacking and rolling allows rolling tocontinue after the aluminum reaches a critical thickness. Although thisprocess is useful for producing some products, it is not necessarilyapplicable for sputtering targets because of material purityrequirements.

Researchers have explored using cryogenic working to increase theforming limits of aluminum alloy sheet panels. For example, Selines etal. disclose a cryogenic process for deforming aluminum sheet in U.S.Pat. No. 4,159,217. This cryogenic process increases elongation andformability at −196° C. In addition, similar work has focussed onincreasing the formability of sheet panels for automotive applications.Key references include: i) H. Asao et al., “Investigation of CryogenicWorking. I. Deformation Behaviour and Mechanism of Face-Centered CubicMetals and Alloys at Cryogenic Temperature,” J. Jpn. Soc. Technol.Plast., Vol. 26, (1985), pp. 1181-1187; and ii) H. Asao et al.,“Investigation of Cryogenic Working. II. Effect of Temperature Exchangeon Deformation Behavior of Face-Centered Cubic Metals and Alloys,” J.Jpn. Soc. Technol. Plast., Vol. 29, (1988), pp. 1105-1111.

Lo, et al., in U.S. Pat. No. 5,766,380, entitled “Method for FabricatingRandomly Oriented Aluminum Alloy Sputtering Targets with Fine Grains andFine Precipitates” disclose a cryogenic method for fabricating aluminumalloy sputter targets. This method uses cryogenic processing with afinal annealing step to recrystallize the grains and control grainstructure. Similarly, Y. Liu, in U.S. Pat. No. 5,993,621 uses cryogenicworking and annealing to manipulate and enhance crystallographic textureof titanium sputter targets.

SUMMARY OF THE INVENTION

The invention is a high-purity aluminum sputter target. The sputtertarget is at least 99.999 weight percent aluminum and has a grainstructure. The grain structure is at least 99 percent recrystallized andhas a grain size of less than 200 μm.

The method of the invention forms high-purity aluminum sputter targetsby first cooling a high-purity target blank to a temperature of lessthan about −50° C. The high-purity target blank has a purity of at least99.999 percent and grains of a grain size. Then deforming the cooledhigh-purity target blank introduces intense strain into the high-puritytarget blank. And recrystallizing the grains at a temperature belowabout 200° C. forms a target blank having recrystallized grains. Thetarget blank has at least about 99 percent recrystallized grains; andthe recrystallized grains have a fine grain size. Finally, finishing thehigh-purity target blank at a low temperature sufficient to maintain thefine grain size forms a finished sputter target.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plot of grain size as a function of annealing temperaturefor cryogenically deformed and recrystallized aluminum.

FIG. 2 is a plot of orientation ratio versus annealing temperature forthe samples of FIG. 1.

FIG. 3A shows the orientation ratios for five comparative target blanksfrom three lots of the conventional thermomechanically processed targetsof Example 2.

FIG. 3B shows the orientation ratios for the fivecryogenically-processed target blanks from three lots of Example 2.

DETAILED DESCRIPTION

It has been discovered that lowering deformation temperature ofhigh-purity aluminum to at least −50° C. lowers the temperature of therecrystallization event and results in a fine grain size. Then heatingthe target blank to a temperature less than 200° C. stabilizes themicrostructure with a minimum amount of grain growth. This processproduces a fine-grained-recrystallized structure having excellentstability at room temperature.

In particular, the process for manufacturing the aluminum targets firstintroduces severe plastic straining at cryogenic temperatures with theintent of increasing the number of viable new grain nucleation sites forsubsequent activation during low-temperature recrystallization. Thisincreases the number of nuclei (N) from intense plastic deformation,reduces the subsequent growth rate (G) of the new grains and results ina reduced recrystallized grain size.

Cryogenically worked pure aluminum has been shown to recrystallize attemperatures as low as −80° C. Furthermore, because grain growthinvolves short range atomic “jumping” across a grain boundary (grainboundary motion), temperature plays an important role in determininggrain boundary mobility. The cryogenic process exploits reduced grainboundary mobility by forcing the recrystallization event to occur at lowtemperatures. Hence, cryogenic working maximizes the ratio of N to G byboth the intense plastic straining and retarded dynamic recoveryassociated with deformation at cryogenic temperatures (increasing N),and the reduced growth rate of newly formed grains by allowingrecrystallization to occur at lower temperatures (reducing G).Maximizing the ratio of N to G allows minimization of the recrystallizedgrain size. Then controlling grain growth during subsequent processingof the target blank into a finished sputter target maintains theresulting minimum grain size.

The broad application of lower-than-normal deformation temperatures byimmersing target blanks in cooling baths immediately prior to formingoperations achieves a highly-worked deformed state. Upon heating to roomtemperature or upquenching, new fully recrystallized grains ofrelatively small size replace the deformed grains.

This process produces high-purity aluminum having at least about 99percent of the aluminum recrystallized. This process is effective fortargets having an aluminum purity of at least 99.999 weight percent. Inaddition, this process is useful for targets having a purity of at least99.9995 weight percent and most advantageously as high as 99.9999 weightpercent aluminum.

The finished grains typically have a grain size of less than about 125μm. For some applications, such as thick monoblock sputter targets, agrain size of less than about 200 μm is acceptable. This represents asignificant improvement in grain size over standard high-purity aluminumtargets. Furthermore, this process can advantageously maintain grainsize to levels less than about 100 μm. Most advantageously, this processmaintains grain size at levels below about 80 μm.

In addition, this process achieves a predominant (200) grain orientationratio. For purposes of this specification, orientation ratio defines therelative proportion of a particular grain orientation in relation tototal grains, expressed in percent as measured perpendicular to asputter target's face. For example, measuring the intensity of an x-raypeak and dividing it by the relative intensity of that peak measured ina random orientation powder standard calculates grain orientation ratio.This ratio is then multiplied by 100 percent and normalized, i.e.divided by the sum of all grain orientation ratios between theintensities and their corresponding relative intensities.

The finished sputter target face advantageously has a grain orientationratio of at least about 35 percent (200) orientation; and mostadvantageously it has at least about 40 percent (200) orientation. Inaddition, the sputter target face most advantageously has a grainorientation ratio of at least about forty percent (200) orientation andabout 5 to 35 percent of each of the (111), (220) and (311)orientations. This combination of a weighted (200) orientation andbalanced (111), (220) and (311) orientations provides the most uniformsputter properties from the sputter target face.

First cooling a high-purity target blank to a temperature of less thanabout −50° C. prepares the blank for deformation. The cooling medium maybe any combination of solid or liquid CO₂, liquid nitrogen, liquidargon, helium, or other supercooled liquid. Advantageously, the processlowers the blank to about −80° C. Most advantageously, the process coolsthe blank to at least about −196° C. or 77 K. The most practicaltemperature for most applications is 77 K (liquid nitrogen atatmospheric pressure).

After cooling, deforming the cooled high-purity target blank introducesintense strain into the high-purity target blank. The deforming processmay include processes such as, pressing, rolling, forging to achievefine grain sizes in pure aluminum. During deformation, it is importantto limit heating of the target blank. Furthermore, it is advantageous toenter an engineering strain of at least about 50 percent into the targetblank. This strain ensures uniform microstructure through the target'sthickness.

Rolling has proven to be the most advantageous method for reducing grainsize and achieving the desired texture. In particular, multiple passrolling, with re-cooling between passes provides the most advantageousresults.

The grains in the target blank recrystallize at a temperature belowabout 200° C. At this temperature at least about 99 percent of thegrains recrystallize. Advantageously, the grains recrystallize at atemperature below 100° C. Most advantageously, the grains recrystallizeat a temperature below ambient temperature. As discussed above,minimizing the recrystallization temperature reduces the target's grainsize.

Optionally, the process includes upquenching the high-purity target to atemperature less than about 200° C. to stabilize the grain size of thehigh-purity target. Most advantageously, upquenching is to a temperatureless than about 150° C. For purposes of the specification, upquenchingis the heating at a rate greater than air heating to ambienttemperature. For example, quenching into alcohol, oil, water andcombinations thereof provides a method for rapid recrystallization.Advantageously, the upquenching is in water. This eliminates the need toprovide major cleaning after the upquenching step. Most advantageously,upquenching occurs by dipping the target blank into agitated water.Agitating the water limits ice formation. In addition, heating the waterto about 100° C. can further improve upquenching. Optionally, the waterbath may contain salt or antifreeze such as ethylene glycol or propyleneglycol for improved upquenching. Since the primary purpose of theupquenching is to “lock in” an excellent grain size and texture on aconsistent basis however, it is important to establish a consistentupquenching process.

The finishing of the high-purity target blank into a finished sputtertarget occurs at a temperature sufficient to maintain the fine grainsize. If the sputter target is finished at too high of a temperature,then the beneficial grain size reduction is lost. Advantageously, thefinishing occurs at a temperature less than about 200° C. to limit graingrowth. Reducing finishing temperature to less than about 100° C.further decreases grain growth during finishing. Most advantageously,the finishing occurs at ambient temperature.

EXAMPLE 1

This Example used full-size CVC-type sputter targets fabricated fromaluminum having a purity of at least 99.9995 percent. The final targetblank dimensions are a diameter of 12.0″ (30.5 cm) and a thickness of0.25″ (0.64 cm). Table 1 provides the manufacturing process specifiedfor this target. In the cryogenic-pressing step (step 2), an operatorimmersed a 5.1″ (13.0 cm) diameter by 3″ (7.6 cm) long workpiece inliquid nitrogen until visible boiling was no longer observed; theworkpiece was then at a temperature of approximately 77 K or −196° C.Re-cooling the cryogenically processed billets between each pressingstep ensured that the imposed deformation took place at a temperature asclose to −196° C. or 77 K as reasonably possible.

Initial cooling and re-cooling steps extended until the workpiece nolonger boiled the liquid nitrogen that surrounded its surface.Immediately after immersing room temperature metals in liquid nitrogen,the liquid adjacent to the metal surface boiled so rapidly that itformed an unbroken gas film that surrounded the workpiece or underwent“film boiling”. During film boiling, the gas barrier limited heattransfer. As the temperature of the workpiece decreased and the metalapproached −196° C., the gas film barrier began to break down and theliquid contacted the metal surface before boiling. Heat transfer wasrelatively rapid during this “nucleate boiling” stage. The boiling rateduring nucleate boiling was significantly higher than that of filmboiling. An interesting observation from the full-scale trials was thatwhen the workpieces approached −196° C., an audible change in boilingstate signaled the transition from film to nucleate boiling.

After pre-cooling was complete, pressing the aluminum between flat diesin two steps (approximately equal reductions) reduced the thickness to afinal height of 1″ (2.5 cm). Between the two reduction steps, immersingthe workpiece in the liquid nitrogen bath re-cooled the work piece toapproximately 77 K or −196° C. In between pressing steps and afterpressing was complete, immediately transferring the workpiece into theliquid nitrogen bath the workpiece prevented the temperature of theworkpiece from exceeding −80° C. This facilitated retaining the maximumstored strain energy imparted by the pressing operations.

In step 3, transferring the workpiece quickly from the liquid nitrogenbath at 77 K or −196° C. to the rolling mill minimized recrystallizationbefore the cryogenic rolling. The cryogenic rolling consisted of takingapproximately 0.040″ (0.10 cm) per pass, with a re-cooling step byimmersion in the liquid nitrogen bath between each rolling pass. As wasthe case with the pressing steps, it is important that the workpiece beimmediately transferred to the liquid nitrogen bath after each rollingpass to ensure that the temperature of the target blank stays as low aspossible. After cryogenic rolling is complete, the workpiece returns toambient temperature. In step 7, epoxy bonding replaced traditionalsolder bonding in order to prevent grain growth that may result fromexposure to the elevated solder temperatures.

It is important to note that because recrystallization of thecryogenically deformed aluminum occurs at a temperature of approximately−80° C., there is no recrystallization heat treatment required before orafter the finish fabrication sequence. For experimental purposes,however, annealing several test pieces at different annealingtemperatures was useful for evaluating the effects that an annealingstep may have on the microstructure and texture of the cryogenicallydeformed aluminum.

TABLE 1 Processing Steps used for Fine Grained Pure Aluminum Target StepDescription 1 Cut 3″ (7.6 cm) length of 130 mm diameter Al 99.9995%billet 2 Cryogenically press 3″ (7.6 cm) to 1.7″ (4.3 cm) to 1″ (2.5 cm)final height 3 Cryogenically roll taking 0.040″ (0.10 cm) per pass to0.325″ (0.83 cm) 4 Water jet cut to diameter of 12.125″ (30.8 cm) 5Machine both sides to thickness of 0.270″ (0.68 cm) 6 Ultrasonicinspection for low inclusion content 7 Epoxy bond to backing plate 8Machine assembly to finished dimensions 9 Ultrasonic inspection of bondintegrity 10 Clean and degrease 11 Inspect and test

Metallographic and X-ray diffraction analyses originated from water-jetcut samples taken from the outer ring of the target blank. FIG. 1 plotsthe grain size results from a sample in the as-deformed condition aswell as several samples that were annealed at temperatures ranging from100 to 200° C. (ASTM E-112 methods determined grain size for theExamples). The measurements reported in FIG. 1 were from samplesannealed 4 hours at their specified temperature, with the exception ofthe first datum, which is the as deformed grain size (assigned anannealing temperature of 20° C.). As expected, increasing annealingtemperatures corresponded to larger grain sizes. The measured grain sizeof the as-deformed sample was 116 μm—this is significantly more finethan standard commercial high-purity aluminum sputter targets.

Referring to FIG. 2, the X-ray diffraction data for the as-deformedsamples (assigned a 20° C. annealing temperature) as well as theannealed samples showed little change in texture for annealingtemperatures up to 200° C.; and all specimens exhibited a 100 percentrecrystallized microstructure having a predominant (200) texture. Thistexture can provide improved sputter performance for fcc metal targets,such as high-purity aluminum sputter targets. Sputter testing of thesetargets also showed improved uniformity in comparison to targetsfabricated by conventional thermomechanical techniques.

EXAMPLE 2

A series of full-scale manufacturing experiments examined themicrostructure consistency of five target blanks from three differentmaterial lots manufactured to the specifications for thermomechanicalprocessing provided above in Example 1. Sectioning the blanks (includingmaterial from each of the three different lots) provided samples formetallographic analysis and determining crystallographic texture. Thetexture analyses and grain size measurements showed a consistent textureand grain size throughout each target. This was consistent from targetto target as well as in all five blanks from the three differentmaterial lots.

Diffraction data collected from the target surface in the erosion grooveregions of each blank (two locations per target) at 1.850″ (4.70 cm) and5.125″ (13.02 cm) distances from the target center provided grainorientation data. Similarly, grain size measurements locations were atnear-surface and mid-thickness regions from three target as follows:near-edge 5.125 in. (13.02 cm); half-radius 1.85 in.(4.70 cm); andcenter per blank.

X-ray diffraction analysis determined crystallographic texture ofthe-target blanks. FIG. 3A shows the XRD results for five conventionallyprocessed high-purity aluminum target blanks from three different lots(Comparative Blanks A-E). The spread of these results are demonstrativeof the difficulties often encountered when trying to control texture inpure aluminum targets. In particular, the crystallographic texture wasdifficult to control and often had a high degree of target-to-targetvariation. Furthermore in-target variation can also be a problem inconventionally-processed pure aluminum targets.

FIG. 3B shows the XRD results for the remaining five cryogenicallydeformed target blanks from the three lots (Sample Blanks 1 to 5). Theseresults illustrated good in-target uniformity as well as excellenttarget-to-target consistency resulting from the cryogenic process.

Table 2 lists the grain sizes measured from the target blanks.

TABLE 2 Grain Size Results (μm) Sample Near Mid- Sample Standard IDLocation Surface thickness Average Deviation 1 Edge 119 127 115 8.50Half- 101 113 Radius Center 116 115 2 Edge 107 94 108 9.90 Half- 108 118Radius Center 120 101 3 Edge 115 132 131 12.90 Half- 146 146 RadiusCenter 121 126 4 Edge 92 113 117 20.89 Half- 135 149 Radius Center 110105 5 Edge 101 112 106 7.36 Half- 110 113 Radius Center 107 94

The overall average grain size from the five blanks was 115 μm; and allsamples contained one-hundred percent recrystallized grains.

EXAMPLE 3

The sequence listed in Table 3 provided the process for fabricating fivetarget blanks from three different material lots. The initial billetshad dimensions as follows: 130 mm diameter×89 mm length and the finishedblanks had dimensions of 305 mm diameter and 11.1 mm thickness.

TABLE 3 Manufacturing Process for Fine-Grain Recrystallized PureAluminum Targets Step Process 1 Cut 5.1″ (13.0 cm)diameter billet to3.5″ (8.9 cm) length 2 Cool part in liquid nitrogen 3 Remove from bathand cryo-press to height of 2.5″ (6.4 cm) 4 Immediately re-cool inliquid nitrogen 5 Cryo-press to final height of 1.5″ (3.8 cm) 6 Re-coolin liquid nitrogen 7 Upquench in water 8 Re-cool in liquid nitrogen 9Cryo-roll 0.100″ (0.25 cm) per pass to a final thickness of 0.550″ (1.40cm) 10 Upquench in water 11 Anneal for four hours at 200° C. 12 Waterjetcut OD to 11.750″ (29.8 cm) 13 Machine both sides to final roughthickness of 0.485″ (1.2 cm) prior to bonding

The microstructures and crystallographic textures of these five blankswere characterized completely for uniformity in-target andtarget-to-target consistency. As in Example 2, the 100 percentrecrystallized targets produced excellent crystallographic orientationand in-target and target-to-target consistency. Furthermore, theseupquenched targets showed an improvement in grain size andmicrostructural uniformity.

Additionally, five other target blanks from the same three material lotswere manufactured with the same process and were solder bonded tobacking plates and finish machined to be made available for sputtertesting. Sputter testing of these targets showed improved uniformity incomparison to targets fabricated by conventional thermomechanicaltechniques.

EXAMPLE 4

Varying several processing parameters used in cryogenic processing ofpure A1 quantified each parameter's effect on grain size. In particular,varying cryogenic pressing strain, cryogenic rolling strain, and heatingrate following cryogenic deformation with the process of Example 3determined each parameter's effectiveness at reducing grain size.

Table 4 shows the experimental matrix as well as the measured responsesand grain size for each of the experiments.

TABLE 4 Pressing Rolling Healing Rate Grain Blank Strain Strain MediaSize 6 0.59 1.17 Water Quench 88 7 0.59 1.17 Slow Heat 118 8 0.18 0.18Water Quench 198 9 1.00 1.00 Slow Heat 112 10 0.01 0.59 Slow Heat 146 110.59 0.01 Water Quench 194 12 0.18 1.00 Slow Heat 98 13 1.17 0.59 SlowHeat 152 14 0.18 1.00 Water Quench 91 15 1.00 0.18 Slow Heat 190 16 1.000.18 Water Quench 182 17 0.01 0.59 Water Quench 118 18 1.17 0.59 WaterQuench 152 19 1.00 1.00 Water Quench 132 20 0.59 0.01 Water Quench 18821 0.18 0.18 Slow Heat 274

The results of Table 4 illustrate that rolling strain had a much morerefining impact on grain size as compared to pressing strain. Theupquenching resulted consistently in a more refined grain size of aconsistent predominant (200) texture. In addition, the grains were 100percent recrystallized.

EXAMPLE 5

Cryogenic processing a monoblock-style sputter targets also providedmicrostructural advantage. A 130 mm billet of pure aluminum was cut to alength of 343 mm and cold upset to a height of 203 mm. Cryogenic upsetpressing the billet, using the cryogenic deformation procedure describedin Example 1, was conducted in four steps (equal percent reductions perstep) to a final height of 102 mm. The upset billet was then cryogeniccross-rolled, using the procedures described in Example 1, to a finalbillet thickness of 46 mm, with 5 mm reduction per rolling pass. Aftercryogenic rolling, upquenching in room-temperature water to rapidly heatthe workpiece back up to room temperature was the final process stepaffecting microstructure. Processing as described above resulted in anaverage grain size of 155 microns and the preferred crystallographictexture illustrated in ambient temperature “annealed” condition of FIG.2. The finished workpiece was directly machined into a finished sputtertarget at ambient temperature to maintain the enhanced microstructure.

The experimental procedure that resulted in the finest possible grainsize consisted of cryogenic deformation followed by “up quenching” ofthe deformed workpiece immediately after rolling from cryogenictemperatures to approximately 50° C. in warm water. The technique oftaking a cold-deformed metal rapidly up to its recrystallizationtemperature results in a more uniform grain size and texture.Apparently, rapid heating increases the number of viable new grainnuclei during the early stages of recrystallization and decreases thetime it takes for the new grains to impinge upon one another to ensure afine-recrystallized grain structure.

The process can fabricate targets of any shape including circular-shapedtargets and sheet-like-rectangular-shaped targets. Furthermore, sincethe targets formed from this process have good strength, they also allowforming the targets directly into monoblock structures. This avoids thecosts associated with bonding a target to a backing plate and increasesthe useful thickness of the sputter target.

With the cryogenic process, it's possible to achieve minimum grain sizesas fine as 50 to 80 μm in monoblock-designed pure aluminum targets.Furthermore, reducing grain size improves sputter uniformity incomparison to conventional high-purity sputter targets that are annealedat temperatures above 200° C. In addition, the process provides a moreconsistent product than conventional wrought methods. Finally, thetarget contains a recrystallized-textured (200) grain that furtherfacilitates uniform sputtering.

Although the invention has been described in detail with reference tocertain preferred embodiments, those skilled in the art will recognizethat there are other embodiments of the invention within the spirit andthe scope of the claims.

1. A method of forming high-purity aluminum sputter targets comprisingthe steps of: a) cooling a high-purity target blank to a temperature ofless than about −50° C., the high-purity target blank having a purity ofat least 99.999 percent and grains having a grain size; b) deforming thecooled high-purity target blank to introduce strain into the high-puritytarget blank and to reduce the grain size of the grains; c)recrystallizing the grains at a temperature below about 200° C. to forma target blank having recrystallized grains, the target blank having atleast about 99 percent recrystallized grains and the recrystallizedgrains having a fine grain size; and d) finishing the high-purity targetblank to form a finished sputter target at a low temperature sufficientto maintain the fine grain size of the finished sputter target.
 2. Themethod of claim 1 including the additional step of upquenching thehigh-purity target to a temperature less than about 200° C. to stabilizethe grain size of the high-purity target.
 3. The method of claim 1wherein the deforming is rolling.
 4. The method of claim 3 wherein therolling is multiple pass rolling and including the additional step ofcooling the target blank between rolling passes.
 5. A method of forminghigh-purity aluminum sputter targets comprising the steps of: a) coolinga high-purity target blank to a temperature of less than about −50° C.,the high-purity target blank having a purity of at least 99.999 percentand grains having a grain size; b) deforming the cooled high-puritytarget blank to introduce strain into the high-purity target blank andto reduce the grain size of the grains; c) recrystallizing the grains ata temperature below about 200° C. to form a target blank havingrecrystallized grains, the target blank having at least about 99 percentrecrystallized grains and the recrystallized grains having a fine grainsize of less than about 125 μm; and d) finishing the high-purity targetblank to form a finished sputter target at a low temperature sufficientto maintain the fine grain size of the finished sputter target at lessthan about 125 μm.
 6. The method of claim 5 including the additionalstep of upquenching the high-purity target to a temperature less thanabout 150° C. to stabilize the grain size of the high-purity target. 7.The method of claim 5 wherein the upquenching is into a liquid bathselected from the group consisting of oil, water, alcohol and mixturesthereof.
 8. The method of claim 7 wherein the upquenching is intoagitated water.
 9. The method of claim 5 wherein the deforming isrolling.
 10. The method of claim 9 wherein the rolling is multiple passrolling and including the additional step of cooling the target blankbetween rolling passes.